ok, lets say you have a php-generated page and you want to add a "Print Me" button. This page has all kinds of colors and images you do not want to display IF the user selects the print button.
So, what you need to do is as the page is being displayed, surround your image links with this:
<? if (!$print_me) { ?>
// image tag here
<? } ?>
Same deal for colors and any other formatting/display thing you do not want to show up if the button is pressed.
Now, in the form tag for the button, simply name the button print_me ... and when a person clicks it, voila! your script will "see" it and not display the images and other stuff (btw: !$print_me means "if the $print_me variable is not available... which means not pressed....)
Let me know if that clears it up.